Concrete vibrator



Nov. 12, 1968 D. CLARK ET AL 3,410,528

CONCRETE VIBRAIOR Filed Oct. 17, 1966 flag arromvsrs United States Patent 3,410,528 CONCRETE VIBRATOR Loris D. Clark and William H. Heinzroth, Dayton, Ohio, assignors, by mesne assignments, to Koehring Company, Milwaukee, Wis., a corporation of Wisconsin Filed Oct. 17, 1966, Ser. No. 587,163 Claims. (Cl. 259-1) ABSTRACT OF THE DISCLOSURE A concrete vibrator has a self-contained motor including a rigid shaft member with one end positioned adjacent an end of a rotatable weight member. An axially extending cavity is formed within one of the members and receives a shaft which is adapted to flex within the cavity and has one end connected to the weight member and its other end connected to the shaft member of the motor.

This invention relates to portable power tools, and more particularly, to a motor driven vibrator adapted to be submerged in fresh concrete.

The present invention has special relation to a concrete vibrator having a self-contained motor such as shown in Patent No. 2,808,238 issued to C. H. Spitler and assigned to the same assignee as the present invention. To provide substantial vibration energy in such a vibrator, it has been found desirable to employ an eccentric weight having substantial mass. On the other hand, it is desirable to confine the weight within a housing of minimum diameter so that the vibrator can be inserted into a narrow chamber, as for example, between the forms for a thin vertical concrete wall. Thus it is common to employ an eccentric weight having substantial length as compared to its diameter.

It is also desirable to minimize the overall length of the vibrator and thus generally the motor and eccentric Weight are arranged in close coupled relationship with a spli'ned connection between the motor shaft and the adjacent end portion of the eccentric weight. Usually, the housing enclosing the eccentric weight is threadably connected to the casing enclosing the motor so that the eccentric weight can be assembled into the housing and the motor assembled into the casing independently, after which the housing and easing are assembled. This construction not only provides for convenient subassemblies but also enables the vibrator to be conveniently serviced after an extended period of use.

It has been found difficult to maintain precise alignment between the rotatable axis of the eccentric weight and the axis of the motor shaft in order to avoid excessive wear of the bearings supporting the eccentric weight and also excessive Wear in the spline connection between the weight and motor shaft. Precise alignment can be held by maintaining extremely close machining and grinding tolerances of the assembled components, however, such tolerances significantly increase the manufacturing cost of the vibrator.

Accordingly, it is a primary object of the present invention to provide a concrete vibrator having a selfcontained motor and including an improved drive connection between the motor shaft and the eccentric weight so that the need for extremely precise machining and accurate alignment between the motor bearing and the eccentric weight bearings is eliminated.

A more specific object of the invention is to provide a concrete vibrator incorporating a drive motor in closely spaced relationship with an eccentric weight and including a flexible shaft connecting the motor shaft to the eccentric weight.

Another object of the invention is to provide a concrete 3,410,528 Patented Nov. 12, 1968 vibrator as outlined above wherein the flexible shaft has sufiicient length to provide a cushioning effect for preventing excessive stresses from being developed Within the motor or transmitted between the rotating parts.

Still another object of the invention is to provide a concrete vibrator as outlined above wherein the eccentric weight includes means for receiving the flexible shaft in generally coextensive relationship, with one end of the flexible shaft connected to the motor shaft and the opposite end of the fiexible shaft connected to the end of the eccentric weight which is more remotely spaced from the motor shaft.

It is also an object of the invention to provide a concrete vibrator including a drive motor and eccentric weight in closely spaced relationship and incorporating a flexible connecting shaft which is economical in construction and can withstand substantial heat without significantly affecting its strength.

These and other objects and advantages of the invention will be apparent from the following description, the accompanying drawing and the appended claims.

In the drawing- FIG. 1 is a partially broken away view of a concrete vibrator constructed in accordance with the invention and showing a power supply cable extending therefrom;

FIG. 2 is a partially broken away axial section of the vibrator constructed in accordance with the invention;

FIG. 3 is an enlarged perspective view of the flexible drive shaft shown in FIG. 2; and

FIG. 4 is a transverse section through the vibrator taken generally along the line 44 of FIG. 2.

Referring to the drawing which illustrates a preferred embodiment of the invention, FIGS. 1 and 2 show a concrete vibrator 10 which includes a cylindrical casing 12 having a forward portion 13 with internal threads. A plug member 14 is rigidly connected to the rear portion of the casing 12 by a circumferential weld and includes a tubular neck 15. An electrical supply cable 16 having leads 17 extends from the neck through a control switch 18 to a plug 19.

The leads 17 supply electricity to a universal motor 20 including a stator 22 retained within the casing 12 and a rotor 23 having a shaft 25. The rear end portion 27 of the shaft supports a commutator 28 which rotates between a pair of brush contacts 29, and is supported by a bearing retaining bracket or housing 30. An anti-friction bearing 32 is mounted within the housing 30 and rotatably supports the rear end portion 27 of the motor shaft 25. Another anti-friction bearing 32 is retained within a forward bearing housing 34 and rotatably supports the forward end portion 35 of the motor shaft 25. External threads 36 are for-med on the forward end portion 35 of the motor shaft. While FIG. 2 illustrates a universal motor enclosed within the casing 12, it is to be understood that for purposes for the present invention, the universal motor could be replaced by an induction motor for use on high frequency AC, or by a pneumatic motor, without departing from the scope of the invention.

A cylindrical eccentric-weight-receiving housing 40 defining a chamber 41 and including a threaded tubular neck portion 42 defining an annular shoulder 43, is connected to the forward end portion 13 of the casing 12 in coaxially aligned relation with the shoulder 43 engaging the end surface of the casing to form a water tight connection therewith. A semi-spherical cap member 45 is secured to the forward end portion of the housing 40 by a circumferential weld 46 and forms an annular shoulder 47 surrounding a grease retaining chamber 48.

The forward end portion of the housing 40 includes a counterbore 49 in which is press fitted a cylindrical bushing 50. Similarly, the rear neck portion 42 of the housing 40 is formed with a counterbore 51 in which is press fitted a bushing 52. The inner cylindrical surfaces of the bushings 50 and 52 are each ground to receive the outer races of one of a pair of anti-friction bearings 54 which rotatably support an elongated weight member 55 having end portions or journals 56 and 57 mounted within the inner races of the bearings 54.

The weight member 55 includes an eccentrically-located tapering portion 59 which has its greatest mass located adjacent the forward journal 56. The eccentricity of the portion 59 of the weight member produces the gyrating effect of the vibrator when the weight member 55 is rotated within the bearings 54.

The inner race of the forward bearing 54 is located on the journal 56 of the weight member by a cylindrical spacing ring 61, and a corresponding ring 62 locates the inner race of the bearing 54 on the journal 57. A spring member 63 is mounted within the rear bushing 52 and is retained by a snap ring 64 seated within an internal groove formed within the bushing 52. The spring member 63 biases the weight member 55 forwardly so that the outer race of the forward bearing 54 seats against the shoulder 47 of the cap member 45.

In accordance with the present invention, a cylindrical bore 65 is formed within the rear journal 57 of the weight member 55 and a cylindrical counterbore 66 of reduced diameter extends from the bore 65 to an elongated cylindrical cavity 68 formed within the central portion of the weight member 55. A socket opening 70, preferably square in cross-section, is formed within the forward journal 56 of the weight member 55 and extends from the cavity 68 to a counterbore 72 formed within the end surface of the journal 56. A plug 73 is press fitted into the counterbore 72 to prevent grease or oil within the chamber 48 from entering the socket opening 70.

A generally tubular adaptor 75 is threaded onto the forward end portion 35 of the motor shaft 25 and seats against the inner race of the adjacent bearing 32. A reduced forward portion of the adaptor 75 extends into the counterbore 66 of the weight member 55 and is similarly formed with a square cross-section socket 77 of the same size as the socket 70 formed within the forward journal 56 of the weight member 55.

An elongated flexible shaft 80 (FIG. 3) formed by overlapping layers of helically wound wire and including swaged square end portions 82, is positioned within the cavity 68 with the rear end portion 82 of the shaft received within the square socket 77 formed within the adaptor 75 and the forward square end portion 82 of the shaft received within the socket 70 formed within the journal 56 of the weight member 55. The plug 73 also forms a stop for the shaft 80. Thus the connection between the motor shaft 25 and the weight member 55 is produced by the adaptor 75 and flexible shaft 80 which directly drives the forward end portion of the weight member where the major portion of the mass is located.

From the drawing and the above description, it can be seen that a concrete vibrator constructed in accordance with the present invention provides several desirable features and advantages. For example, by locating the longated flexible shaft 80 coextensive with the weight member 55 within the cavity 68, the weight member is driven substantially at its forward end through a flexible drive shaft without affecting the closely spaced relationship between the rear end portion or journal 57 of the weight member 55 and the forward end portion 35 of the motor shaft 25. Thus by locating the flexible drive shaft 80 within the cavity 68, there is no increase in the overall combined length of the weight member 55 and motor 20.

As a result of the flexible drive provided by the flexible shaft 80, it has been found that it is no longer necessary to maintain extremely close machining and grinding tolerances of the forward end surface of the casing 12 and the annular shoulder 42 in relation to the bearing retaining surfaces formed within the bushings 50 and 52 and within the motor bearing brackets or members 30 and 34.

Thus the cost of manufacturing the vibrator is significant ly reduced.

Other advantages provided by the flexible shaft 80 are that the shaft can be economically produced and, in addition, provides a cushioning effect which substantially relieves the stresses transferred from the weight member 55 to the motor 20. This cushion effect also prevents excessive wear between the square end portion 82 of the flexible shaft 80 and the mating sockets 70 and 77. Furthermore, the flexible shaft 80 eliminates excessive stresses from being imposed on the bearings 54 supporting the'weight member 55.

While the drawing shows a preferred construction of the invention wherein the flexible shaft 80 is mounted within a cavity 68 formed within the weight member 55, it is within the scope of the invention to form a cavity within the motor shaft 25 so that a flexible shaft therein connects the rear end portion 27 of the motor shaft 25 and the rear journal 57 of the weight member 55, the basic concept of the invention being that the flexible shaft 80 is coextensive with either the motor shaft 25 or the weight member 55 or is located in a position where it is partially coextensive with both the weight member 55 and motor shaft 25, that is, intermediate the end portion 27 of the motor and the end portion or journal 56 of the weight 55.

While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. In a concrete vibrator including a casing containing a motor (20) having a rigid shaft member (25) with a first end portion (27) and a second end portion bearing means (32) rotatably supporting said end portions of said shaft member, a housing having one end portion (42) connected to said casing and an enclosed opposite end portion an eccentric weight member within said housing and having a first end portion (56) and a second end portion (57), bearing means (54) rotatably supporting said end portions of said weight member on an axis substantially coaxial with the axis of said shaft member, and said second end portion (57) of. saidweight member being disposed in close adjacent rclationship with said second end portion (35) of said shaft member, the improvement comprising means defining an axially extending cavity (68) within one of said members intermediate the corresponding said first and second end portions, an elongated flexible shaft (80) extendingwithin said cavity and having first and second end portions (82), a substantial portion of said cavity having a cross-sectional area greater than the cross-sectional area of said flexible shaft to permit flexing of said shaft within said cavity, means and 82) disposed on one end of said cavity for connecting said first end portion of said flexible shaft to said first end portion of said member having said cavity, and means (77 and 82) disposed on the other end of said cavity for connecting said second end portion of said flexible shaft to the other said member for preventing wear of said bearing means due to misalignment between said motor shaft member and said weight member while minimizing the overall combined axial length of said motor and said weight member.

2. A vibrator as defined in claim 1 wherein said second end portion of said weight member forms a tubular journal, said bearing means including an anti-friction bearing rotatably supporting said journal, said means connecting said second end portion of said flexible shaft to said motor shaft member including an adaptor mounted on said motor shaft member and projecting into said tubular journal of said weight member with annular clearance space between said adaptor and said journal, and socket means connecting said second end portion of said flexible shaft to said adaptor.

3. A vibrator as defined in claim 1 wherein said first end portion of said weight member has substantially greater mass than said second end portion of said weight member, said cavity extends axially within said weight member between said first and second end portions, said first end portion of said flexible shaft being connected to said first end portion of said weight member, and said second end portion of said flexible shaft being connected to said second end portion of said shaft member adjacent said second end portion of said Weight member.

4. A vibrator as defined in claim 3 wherein said flexible shaft includes overlapping layers of helically wound wire, said first and second end portions of said flexible shaft each having a square cross-sectional configuration, means forming a square socket Within said first end portion of said weight member for receiving said first end portion of said flexible shaft, and said means connecting said second end portion of said flexible shaft to said motor shaft member including means forming a square socket for receiving said second end portion of said flexible shaft.

5. The vibrator as defined in claim 4 wherein said bearing means for said Weight member include anti-friction bearing means rotatably supporting said end portions of said weight member, said first end portion of said weightmember being disposed adjacent said enclosed end portion of said housing, plug means within said first end portion of said weight member for closing said socket and forming a stop for said first end portion of said flexible shaft, means forming a bore within said second end portion of said weight member and extending to said cavity, and said connecting means for said flexible shaft including an adaptor positioned within said bore and threadably connected to said second end portion of said motor shaft member.

References Cited UNITED STATES PATENTS 1,678,335 7/1928 Gaston.

2,137,328 11/1938 Bissell.

2,492,431 12/ 1949 Kroeckel 259-1 2,501,158 3/1950 Chilcott 259-1 2,808,238 10/1957 Spitler 2591 2,844,041 7/1958 Beijer et a1. 74-87 3,283,598 11/1966 Barnes 259-1 XR ROBERT W. JENKINS, Primary Examiner. J. M. BELL, Assistant Examiner. 

